HOULTON — Maine jurors who convicted a man last week of killing a 10-year-old boy and two men rejected his insanity defense on Thursday, meaning he now faces at least 25 years in state prison and could get up to life behind bars.

The Superior Court jury heard two days of conflicting expert testimony about Thayne Ormsby’s state of mind at the time of the June 22, 2010, killings. A sentencing date has not yet been set.

Ormsby, 23, confessed to state police to fatally stabbing Jeffrey Ryan; Ryan’s son, Jesse; and family friend Jason Dehahn at Ryan’s home in Amity. He said he wanted to kill the elder Ryan because he thought the man was a drug dealer, and he killed Dehahn and the boy to eliminate potential witnesses.

Jurors convicted Ormsby of three counts of murder last week. Because of Ormsby’s insanity defense, they heard additional testimony this week that could have led to him being sent to a psychiatric hospital instead of prison.

A psychologist testified for the defense that Ormsby was delusional at the time of the killings and that he’d been abused as a boy. But another expert testified for the state that Ormsby wasn’t delusional and that he knew what he was doing was wrong.

Deputy Attorney General William Stokes said Ormsby was fascinated with killing and decided to kill Jeff Ryan because he thought Ryan was a bad man.

“He didn’t think Jeff Ryan was too nice of a guy, so he put his thoughts into action,” Stokes said.

Ormsby’s actions may not have been rational but they didn’t meet the legal requirement for an insanity defense after he killed the three, burned his clothes and Ryan’s pickup truck to conceal evidence, and traveled to New Hampshire, where he was ultimately arrested, the prosecutor said.